This invention pertains to improvements in counterpressure container filling devices.
In one known type of counterpressure filling device there is the conventional fluid valve and gas valve coupling a tank containing the liquid to a container such as a bottle which is to be filled. Upward movement of a control member arranged at the upper end of the return gas tube first releases the fluid valve so that if equal pressure in the tank and container prevails the valve will open automatically by a spring. Additional upward movement of the control member forcibly opens the gas valve. In the reverse case of downward movement of the control member the gas valve and then the fluid valve are forcibly closed. With this known container filling device it is not possible to simultaneously hold the fluid valve forcibly closed and the gas valve forcibly open.
To make it possible for the liquid and pressurizing gas that is expelled from the container to return during the end phase of the filling process the known container filling device provides the gas valve stem with a spring loaded back pressure valve that at a certain over pressure in the container being filled or in the return gas tube opens the path to the storage tank automatically. For this device, the over pressure of the gas supply relative to the pressure in the storage tank needs to be comparatively large in order to assure positive opening of the back pressure valve which acts as a choking restriction.
The pressure spike generated upon opening of the back-pressure valve thus causes a considerable disturbance of the liquid in the storage tank and in the container being filled. Disturbances can create problems, for example, they can cause an undesirable increase in oxygen absorption or release of carbon dioxide. Another problem is that filling height is not as precise as should be obtainable with a counterpressure system because more or less liquid below the level of the lower open end of the return gas tube is blown through the return gas tube and back into the tank.
Similar conditions prevail for other known container filling devices of this general prior art type which differ from the container filling device only in the design of the non-return stop valve as in U.S. Pat. No. 3,209,794.
In another known container filling device a gas valve with a hood-like valve body is located at the upper end of the return gas tube to control only the flow of the displaced pressurizing gas as the container is filled while another separately controlled valve pressurizes the container. This is illustrated in U.S. Pat. No. 2,617,575. The gas valve on the return gas tube is coupled with the forcibly-closable fluid valve in such a way that it is always opened when upon pressure equalization between tank and container the fluid value opens automatically by means of a spring. Closing of the gas valve upon forcibly closing the fluid valve is achieved solely by the weight of the hood-like valve body. The gas valve, thus, can not be forcibly closed or be kept forcibly closed. In the end phase of the filling operation the hood-like body acts as a back-pressure valve when gas is blown into the tank in order to remove any liquid that is higher than the lower tip or end of the return gas tube in the container. This known container filling device has the same inadequacies as the previously described devices.